Photo-Reproductive Processes Used for the
Duplication of Architectural and Engineering Drawings: Creating
Guidelines for Identification

Judith Reed, Eléonore Kissel, and
Erin Vigneau

Abstract

The New York Botanical Garden Library's collection of
architectural drawings consists of about 130,000 working drawings,
dating between 1880 and 1960, containing original drawings on linen
and paper and an assortment of photoreproductive processes. As the
Lord and Burnham Collection is a research collection, the prints are
of equal value to the originals and must be retained.

Little information on photoreproductive processes was available
from published sources or professional colleagues in the fields of
paper and photo conservation. Some sources indicated that these
processes, when stored together, might cause degradation to other
materials and to each other. Subsequently, the authors began to
pursue information regarding identification of these prints, in
order to make decisions about segregation and housing.

Information was collected on the description and appearance,
synonyms, history and use, technical information, manufacturing
data, and details about degradation and storage for 14
photoreproductive processes. As a result, criteria for visual
identification was developed, originally intended for the use of the
NYBG conservation staff. Subsequently the authors decided to make
the information available for use by people who are responsible for
collections of architectural drawings, but who do not have access to
sophisticated analytical equipment or facilities. This paper will
describe the criteria which have been developed for visually
identifying photoreproductive processes found in architectural
archives.

Introduction

The New York Botanical Garden Library's collection of
architectural drawings of glasshouses contains drawings on paper,
linen, and tracing paper and a variety of photoreproductive print
processes. During the 1980's, the drawings were transferred to the
Library, which now holds title to the collection. It was donated by
the Lord & Burnham Corporation, premier designers and builders of
greenhouses and conservatories in the United States during the last
half of the nineteenth century and the first half of the twentieth
century.

The collection had suffered from poor storage conditions while
held by the Lord & Burnham Corporation. The drawings arrived at the
Botanical Garden stored in old folders; some housed in damaged or
inadequate flat files, others simply in unsightly piles.
Fortunately, only a few drawings were rolled and most were small
enough to be stored flat and unfolded. It became clear that the
order of first importance was to provide proper housing for the
collection as soon as possible. A grant from the New York State
Library Conservation/Preservation Program, several years ago allowed
the in-house conservation staff and the Northeast Document
Conservation Center to carry out full conservation treatment and
rehousing of about 1,000 of the drawings. By the conclusion of this
project, the staff had become aware that such labor-intensive,
time-consuming efforts carried out on the entire collection would be
impractical. Therefore, conservation efforts were redirected toward
the more immediate goal of stabilizing and properly rehousing the
entire collection.

In order to maintain the original order of the collection, it was
decided to retain the numbering system assigned by the Lord &
Burnham Corporation. These numbers refer to all the drawings
relating to one specific project or building. The same numbering
system was used by the Company for its business records and
correspondence, materials which are part of the complete Lord &
Burnham Collection, held by the Library. Having arrived at this
decision, it became evident that all the drawings for a project,
whatever the support, medium, reproductive process, or dimension,
should be housed together to facilitate research and access.

To provide further access to the collection the Research
Librarian, Bernadette Gallery, and the conservation staff designed a
preservation and access database, which provides an inventory and
finding guide to the collection, as well as recording the various
types of supports, media, and processes in the collection, and the
future conservation treatment needs of the drawings.

The L&B Collection consists primarily of working and
engineering drawings, rather than attractive or artistic renderings.
In the late nineteenth century the need for architectural drawing
reproductions increased tremendously with the advent of new
construction methods, which relied heavily on teamwork and often on
the reuse of a basic original plan; skyscrapers, for instance, as
well as standardized building units erected in newly developed
suburbs. Consequently, major collections of architectural archives
often contain a large percentage of prints. Therefore, the
photoreproductive prints, which often indicate changes in original
design, are of equal importance to the original drawings and must be
retained as an integral part of the collection.

Fig. 1. Multiple layers of polyester film
inserts segregate different types of prints from each other and from
drawings while keeping all of the plans from an original group
intact

Since the order of the L&B Collection is basically
chronological, more and more types of photoreproductive processes
began to show up as the rehousing project progressed. The staff was
aware that an alkaline environment, although desirable for storage
of the original drawings on paper or cloth, was unwanted for photo
processes. Questions began to arise. Would various photo processes
cause one another to degrade when in contact? How should the
processes be separated from the other drawings and from one another,
while still being kept intact as a collection? Polyester film
inserts within the alkaline-buffered folders solved the problem of
separating the drawings from the prints and isolating the
photographic processes from direct contact with the alkaline folders
(Figure 1).

However, it required the teamwork of the conservation staff to
research the information needed to resolve the other questions.
Their varied backgrounds in training and experience complemented one
another well, providing a combination of librarian, library
materials conservator, bookbinder, paper conservator, printmaker,
and photographer.

A Conservative Approach: The Decision to Segregate

During the initial project, the conservation staff had identified
two blue and white print processes, cyanotypes and diazotypes. When
Erin Vigneau began to work on the rehousing project of the L&B
Collection prints began to appear which had not been found
previously. A brown print with white lines surfaced, as well as a
black print with white lines which had a shiny photo-paper like
coating. Ms. Vigneau recognized these, from her experience with
photography, printmaking, and photoreproductive processes, as a Van
Dyke brown print and a silver based Photostat, respectively. Groups
of drawings which contained photo reproductions from the 1950's had
several prints with warm brown lines on a dirty white ground. These
seemed comparable to diazotypes. The staff confirmed with a
practicing architect that these prints were called sepias and were
processed and used similarly to diazotypes.

Ms. Vigneau knew from processing cyanotypes and Van Dyke prints
that the two should not be washed in the same final rinsing bath;
potassium ferricyanide in the cyanotype chemistry acts as a
bleaching agent to the silver contained in the Van Dyke print. This
led the staff to the question of whether or not dry cyanotypes and
Van Dyke brown prints might affect each other when stored
together.

During the rehousing project degradation to drawings on tracing
paper, induced by contact with coated and uncoated sepia prints, was
noticed. Coated sepias ooze a greasy substance onto the adjacent
paper drawings. Uncoated sepias transfer a reddish stain onto nearby
documents, which bleeds through several layers of drawings. Viewing
these degradations, the staff reasoned that all diazotypes might be
affecting contiguous documents by being housed along side them.

Concerned about these mounting questions, Ms. Vigneau began to
seek more information on these photoprint processes, but little was
available, especially on historical print processes. Even texts
which did document the many and varied historical techniques for
photoreproduction had little or no concrete descriptions of visual
characteristics to use in identification. Photo conservators that
were contacted knew only about cyanotypes which were used as a
method for reproducing photographic images. The staff did consult
with Lois Olcott Price, who is working on a definitive manuscript
about early architectural archives, their history, and
recommendations for storage and treatment. She has been unstintingly
generous in her recommendations and confirmations throughout this
research, and solutions to some of the identifications have been
worked out together with her.

It was known that some prints had been made with metals and some
with dyes, and that some were processed in ammonia or sodium
thiosulfate solutions. Many prints in architectural archives are not
processed with any archival future in mind, as they are seen as
interim stage prints or duplicates. It became apparent that many of
these processes were possibly exuding chemical by-products to
drawings and other prints. At this point, having little information
about these reproductions, Ms. Reed and Ms. Vigneau chose to take
the conservative approach and segregate each type of print. Solving
the questions about identification, for the purposes of separation,
was now an important part of the rehousing effort.

The Research Component

Eléonore Kissel joined the Lord and Burnham project at the
start of her Kress Internship in Paper Conservation, when many of
the decisions regarding the rehousing of the collection had already
been made. She spent the first three months of her internship
rehousing the documents, after which she proposed a research project
directed towards the identification of the printing processes by
which architectural drawings are duplicated. The basis of the
project was to be a search of the existing literature, followed by
the development of a guidebook, with photographs of prints from the
L&B Collection to illustrate the written guidelines for
identification. Ms. Kissel began to look for bibliographic
references, first in the field of conservation, then in the
professional literature available to architects, and finally in
historical printing and photography trade magazines and catalogs. It
soon became clear that all of these sources would need to be
researched in order to find all possible information about these
printing processes that had been used to duplicate architectural
drawings. Such prints have been thought of throughout their history
as merely expendable utilitarian copies and thus have not received
as much attention or care as the original drawings from which they
were created. Early trade catalogs proved to be a rich primary
source for the information being sought.

The staff knew that many other conservators and curators were
interested in the preservation of architectural drawings and
reproductions. In contacting them for advice, they led the staff to
sources they had not been aware of. Ms. Kissel created a database of
bibliographic references, to which she added French and Canadian
references frequently not found in American publications. By the end
of her internship the bibliography had become quite substantial.
Visits to institutions in which architectural or design records are
housed and conserved, such as the Library of Congress, the American
Institute of Architects, and the Canadian Center for Architecture,
proved to be informative. A trip to the Frederick Law Olmsted
National Historic Site was important and useful, not only because of
the span of the drawings collection, but also because of the
opportunity to observe the early twentieth century printing
equipment still in place at the Olmsted Site.

The L&B Collection: A Primary Source for
Photoreproductions

The major problem with the information gathered continued to be
the almost complete absence of images or visual descriptions of the
reproductive processes. In addition to the unpredictable appearances
of the prints themselves, confusion over the nomenclature applied to
these printing processes made the research more complex. For
example, documents with brown lines on a light background have been
called at least half a dozen different names. In addition, the term
"blueprint" has been applied, over time, to three distinctly
different processes. Even when there was information available about
the supports and sensitizing solutions used in the manufacture of
reproductions, it was difficult to imagine, short of making an
actual photoreproduction, what each print might look like. And even
if it could be determined what they would look like immediately
after their manufacture, they would look very different a few
decades later, having been exposed to light, used extensively, and
often housed in less than ideal conditions.

It is for this reason that the staff turned mainly to the L&B
collection for actual examples of prints which have been subject to
heavy use and poor storage conditions. Over time, they identified
and isolated fourteen different types of prints, produced between
the mid-nineteenth century and the 1980's. The names of these appear
below:

Aniline prints

Cyanotypes

Diazotypes

Electrostatic prints

Ferrogallic prints

Gel-lithographs

Hectographs, (handmade)

Pellet prints

Photostats

Sepia prints

Silver halide prints

Stencil duplicating (mimeographs)

Spirit duplicating (hectographs, machine made)

Van Dyke prints

For each process the following information was collected: trade
names and commonly used nomenclature; history and use of the process
(with probable dates); supports and chemicals used in the
manufacturing process; subsequent changes in the reproductions over
time; and the means for preventing further degradation by using the
appropriate housing procedures.

The staff had discovered, through daily handling of the prints
during the rehousing effort, and through data compilation, several
instances in which it was detrimental to house different processes
together. To give only a few examples:

Diazotypes off-gas phenolic by-products, which are harmful to
other types of documents as well as to themselves.

Diazotypes are frequently developed with ammonia fumes; they
continue to off-gas alkaline vapors which may affect documents which
are alkaline-sensitive. Some documents may be sensitive because of
their constituent materials, others because they have become highly
acidic over time; e.g., cyanotypes ("blueprints") and Pellet prints
are made of two pigments, Prussian Blue and Turnbull Blue, that may
turn brown if housed in a closed alkaline environment; in the case
of a flood, acid/base reactions may occur if a highly acidic
document, such as a ferrogallic print, is housed with a
diazotype.

Diazotypes manufactured after the 1930's may contain thiourea
(used as a stabilizing agent) and should not be housed in contact
with silver based photographic prints. Thiourea, a sulfur containing
product, may cause the deterioration known as "silvering" or
"mirroring" on silver based prints such as Photostats. Note,
however, that this alteration could also be due to poor
environmental conditions, in particular a polluted,
sulfur-containing atmosphere.

These discoveries reinforced the validity and importance of the
conservative approach to housing that had prevailed since the
beginning of the project; when in doubt, isolate to eliminate the
risk of contact degradation. However, in order to isolate and reduce
risk, the questions of identification needed to be solved. It was
important that simple, visual and tactile criteria be established.
The authors wanted to enable the Library staff, and people with
architectural drawings and prints under their care, to be able to
identify the process used to produce the prints if they took the
time to examine them closely. Conclusive identification would allow
proper housing to be provided and promote the best chance for the
long term preservation of the archive.

Criteria For Identification

As Ms. Kissel's research progressed, she and Ms. Vigneau became
more adept at identifying the processes that were found in the
L&B collection. They found that there were specific traits,
marks and characteristics which could be consistently observed and
compared during investigations. As the research was compiled into
the document which has become A Manual For The Identification
Of Architectural Archives Reproductions, a glossary of
terminology was created to explain the methodology. How could the
procedure followed in investigations be described? The successive
paragraphs detail the many indicators used to identify a print
through visual inspection.

First, what is the nature of the support? Is the print
support paper, cloth, or plastic film? Some processes were produced
only on paper, or only on linen, and some were made on a variety of
supports.

An early indicator is the color of the image line. Even
though two prints with white backgrounds and blue lines appear very
similar, they may be different processes and can potentially harm
each other if housed together. To correctly identify two like
processes with blue lines on a white ground one must look at the
nature of the image line. By viewing the lines close up, through a
magnifying loupe, variations in the two types of blue lines can be
seen. A Pellet print, will have a deep Prussian blue line with a
hard edge. The line in a diazotype will be softer and hairier, with
the characteristic ability to copy a soft pencil line with
consistency.

Lines can appear to be sitting upon the surface of the support or
imbedded into the fibers, making them appear as if dyed. The line of
the Pellet print will appear as if the fibers are stained, that the
color is imbedded in the paper, whereas the lines of the diazotype
will subtly seem to be resting on the surface. Diazotype lines are
created from aniline dyes and will not be raised above the surface
like a paint line but the color will not sink deeply into the fibers
of the paper.

In contrast, lines in wet processed ferrogallic prints and
aniline prints will be so deeply imbedded into the paper that they
will appear almost as if they are below the surface. This is due to
the acidic development process that they go through, where the
opening action of the acid on the cellulosic fibers (paper or linen)
drives the chemical lines deep into the support. In addition,
ferrogallic and aniline images often have lines and ground of such a
close value that the overall image is of very low contrast.

After checking the image line, look at the color of the
background. Is it white, dirty white, blue, green, tan? In
identifying some prints, such as aniline prints, this one element, a
green background, can be enough to point you to a conclusive
identification.

Fig. 2. Two diazotypes showing the
distinct difference between the residually toned recto and white
verso

Another clue in successfully differentiating prints is the
appearance of the ground. Prints may have a flecked, dirty
white ground or a smooth white background on which the image lines
appear. A background with a faint, even colored tone, may also be
found; one likely example is the ground of a Pellet print. The
residual tone from the sensitizing solution of diazotypes will
remain on the image/recto side because the print is not rinsed in
its processing. The verso will remain an unstained, uniform white
(Figure 2). The difference between the
toned recto and the white verso is a good indicator, along with
other clues, in the conclusive identification of diazotypes.

Another characteristic to observe closely is the appearance
of the surface. The fibers of a paper support can change when a
print has been aqueously processed. Prints that have been processed
by vapors alone retain their original calendered surface while those
that have been through one or several wet baths will have a more
raised surface appearance, the fibers of the support having expanded
and contracted in processing. One of the reasons that diazotypes are
still one of the most commonly used copying processes is that, by
using an essentially dry development process, the scale of the copy
remains identical to the original. Prints which are
photomechanically produced such as gel-lithos and hectographs will
also be found to have a hard calendered surface typical of a support
which has not been through a wet step in its development.

Along with these signs, the condition of the support can
provide valuable information when trying to identify a print.
Ferrogallic prints are often brittle and degraded from the acidic
developing bath to which they have been subjected. A See-Bee (or
C.B.) print, which has a hard black line deposited on the surface of
a coated linen support, may also appear degraded, due to an alkaline
bath used in its processing. These clues, along with descriptors,
such as the color of line and ground, type of support, and
appearance of line, can add up to a conclusive identification.

Fig. 3. A tracing which, when removed from
its original housing, exhibits typical greasy stains due to contact
with an adjacent waxed sepia print

When removing photoreproductions from the storage conditions in
which they may have resided for many years, characteristic
degradations to the prints themselves, or to adjacent
materials, may be observed. It is important to be aware of these
degradations and to record them. They may augment the other
indicators and determine the final analysis. Diazotypes frequently
exhibit an edge discoloration, caused by the residual phenolic
products, which oxidize and cause the paper support to discolor. A
yellowing is present, more pronounced along the edges of the print,
and occurs only on the image side where the sensitizing solution was
applied. Degradation to adjacent drawings can be a clue in the
identification of sepia prints. Uncoated sepia prints impart a
reddish pink discoloring onto contiguous tracings. Sepia prints,
impregnated with waxy products for increased transparency, create
greasy looking stains on adjacent drawings (Figure 3). Both of these forms of contact
degradation can migrate through several layers of nearby
tracings.

Misleading factors in identification include odor and dates on
prints. It is true that some documents have a strong characteristic
odor, especially diazotypes which are processed in ammonia vapors
and not washed afterward, however, the staff found that the smell
can transfer to almost all neighboring documents, making it hard to
discern which of many prints may be the original culprit. The date
which appears in the reproduction is often a misleading factor in
identifying a print. Unless the date is written onto the front of
the print or a stamp of receipt with a date is present (perhaps on
the verso), the date written on the original drawing, which is
reproduced in the print, could possibly be years apart from the time
the print was made. The date of the original drawing allows us to
determine only that the print was made after that date but not
necessarily on that date.

Fig. 4. One of the "Ozalid" watermarks,
photographed while backlit

Stamps that may be found on the verso include manufacturers trade
names for photo print processes and may be used as an additional
tool in the identification of a document. Names found on prints have
included whiteprint, dyeline, ordoverax, rectigraph, and brownline,
among others. The research completed by the authors attempts to
cover as many trade names and industrial vernacular terms as
possible. Often common names, such as blueprint and brownline, have
been used in the trades to refer to different processes. Trade names
written and stamped are not always conclusive but can add to the
many clues used to make an identification. One specific patented
diazotype paper, Ozalid, includes a chemically manufactured
watermark (Figure 4), which is an explicit
mark to use in identifying it as a diazotype.

In review, a list of the basic criteria is as follows: nature of
support, color of ground, color of line, nature of line, nature of
ground, surface appearance, condition of support, characteristic
degradations (to prints themselves and to adjacent documents),
manufacturer's stamps and trade names, and the misleading indicators
of odor and dating. It must be stressed that no one factor can be
used in making a conclusive analysis. A detailed description of the
process, historical information about it, its manufacture and its
subsequent changes and degradations should be considered before
determining a final identification.

A Manual for the Identification of Architectural Archives
Reproductions

The aforementioned criteria were developed over a period of more
than a year while the staff rehoused and surveyed 58,000 drawings
and prints. The manual containing this research was originally
created for the use of the conservation staff during the rehousing
of the remaining approximately 72,000 drawings. Investigation
sometimes led the staff to correct or revise decisions about
identifications that had been made previously. The conservation
survey database allowed them to backtrack through hundreds of groups
of drawings and re-segregate prints which had been mistakenly housed
together. It is their hope that others will be able to benefit from
these investigations and mistakes and use their experiences to aid
in the ability to care for collections of architectural
drawings.

The staff began to share information related to their research by
answering inquiries sent to them by colleagues. They also gave
hands-on workshops to curators, conservators, technicians, and
archivists dealing with architectural drawing reproductions.
Contemporaneously Ms. Kissel and Ms. Vigneau prepared the manuscript
for A Manual for the Identification of Architectural Archives
Reproductions which they hope to publish in the near future.
It is designed for individuals who care for architectural records
collections but do not have access to sophisticated analytical
facilities. Using low magnification, the visual criteria devised
should assist in the identification of many prints which may be
found in architectural drawing collections. However, several
duplicating processes were in use for very short periods of time,
and a mystery print is likely to be found in every collection. Most
commonly used historical printing processes are included in the
manual, as well as some techniques currently in use for duplication.
Several processes are still being investigated in the hope of
finding concise information which will lead to accurate
identification and care. The manual will be illustrated with color
reproductions of prints, both general views and details. Again and
again, the most limiting factor in the research was the lack of
illustrations as well as written descriptions with which to compare
the prints found in the L&B collection.

Flow-Chart for the Identification of
Architectural Archives Reproductions of Drawings and
Documents

Fig. 5. Page of the flowchart from A Manual
for the Identification of Architectural Archives
Reproductions

Figure 5 shows a section of the flowchart,
which will appear in the Manual, designed for the identification of
the prints. It uses simple questions that can be answered just by
looking at the print, such as: "what is the nature of the support",
"what color is the line", and "is the ground spotless or does it
seem dirty", etc. The Manual will use color reproductions to
illustrate each process to aid the user in identification.

Conclusion

The authors firmly believe that the proper identification of
photoreproductive prints, and the knowledge of their constituent
elements, is a crucial component of every aspect of the preservation
of architectural collections: records storage, access, exhibition,
duplication and conservation. Knowing what elements a print consists
of determines its use and care; it is thus a responsibility of every
collection manager or conservator to understand how reproductions
are produced and should be cared for. They are frequently the only
documents that still relate to destroyed or damaged architectural
structures.

Acknowledgements

The authors would like to thank Mr. John F. Reed, Director, NYBG
Library for his support, Lois Price for her expertise and advice,
and Wendy Gogel and her staff from The Frederick Law Olmsted
Historic Site for their cooperation in testing our research. The
research was made possible in part through a grant from The Samuel
H. Kress Foundation which supported a six month educational
internship in which Ms. Kissel participated.

Publication History

Received: Fall 1995

Paper delivered at the Book and Paper specialty group session, AIC
23th Annual Meeting, June 4-1, 1995, St. Paul, Minnesota.

Papers for the specialty group session are selected by committee,
based on abstracts and there has been no further peer review. Papers
are received by the compiler in the Fall following the meeting and
the author is welcome to make revisions, minor or major.